Non-meniscus forming orifices

ABSTRACT

Means for freeing an opening in a base member from blocking fluids which may normally form a meniscus over an opening including a notch in the base member with a wide portion substantially tangent to the sides of said opening and with converging edges from said wide portion. The notch may include a V-shaped groove in the base member having a depth decreasing from said wide portion with converging edges of sharp definition. The notch may be aligned with the converging edges in the direction of forces tending to clear the fluid from the opening.

United States Patent [151 3,695,384

Schiess [451 Oct. 3, 1972 NON-MENISCUS FORMING ORIFICES PrimaryExaminer-Benjamin A. Borchelt 72 Inventor: Marcel c. Schiess, 703 QuincyN.E.,

Albuquerque, 87] lo Attorney-Roland A. Anderson (22] Filed: Sept. 25,1970 [57] ABSTRACT PP- Nod 75,384 Means for freeing an opening in a basemember from blocking fluids which may normally form a meniscus over anopening including a notch in the base member with a wide portionsubstantially tangent to the sides |5x| Field of Search ..239/310, 318;340/34, 38 P, said converging edges fmm Said 340/50 190 343/720 872-l8l/05 R 05 The dude a P groove in the base member having a depthdecreasing from said wide portion with converging edges of sharpReferences Cited definition. The notch may be aligned with the con-UNITED STATES PATENTS verging edges in the direction of forces tendingto 2,948,480 8/1960 Budwig ..239/3l8 clearhe mm! mm the pemng 2 Claims,4 Drawing Figures SEISMIC ACOUSTIC SURVEILLANCE VERIFICATION SYSTEMsvs'rsm PATENTEDum 3 1912 3,695,384

FIG. 2

% fiz yl/lfl Q N o o 4 N N m 11 42 w I K 44 SEISMIC ACOUSTIC SURVEILL EVERIFICA N SYSTE SYSTE INVENTOR. MARCEL C. SCHIESS NON-MENISCUS FORMINGORIFICES.

BACKGROUND OF INVENTION Orifices or ports or other similar openingswhich are used in an environment containing liquids are subject toblocking by the liquid when the opening size is sufficiently small inrelation to the surface tension of the liquid. When the opening size issmall enough so that the liquid can form a meniscus in the opening, theopening may be blocked or obstructed by the meniscus and prevent passagetherethrough of gas or air or of sound waves and the like or otherwiseinhibit utilization of the opening.

A particularly difficult liquid to deal with under such circumstances iswater because of its high wetting ability and high surface tension.Therefore, applications which utilize orifices in an area which may besubjected to rainfall or to condensation from humidity or the like maybe susceptible to such meniscus blocking.

There are various surveillance systems or devices which are used fordetecting or monitoring man-associated intrusions (such as personnel orvehicular traffic) within certain controlled areas, for example, incommercial establishments or private residences and security restrictedor military areas. Some of these surveillance systems many monitorseismic signals and then attenipt to identify and determine whether theyare man-associated. It may be very difficult to identify or distinguishman-associated seismic signals from other extraneous disturbances undersome circumstances, such as seismic signals generated by wind, rain,thunder and the like. Because of this, it is desirable in many instancesthat there be some verification of the identification of the seismicsignals as man-associated. Such verification may be achieved byincorporating an acoustic sensing device with the seismic surveillancesystem and the acoustic sensing device energized whenever a suspectedman-associated intrusion is detected by the seismic system. Such maythus provide an acoustic verification of the man-associated intrusion.

It will be apparent that such a system may be used under a wide range ofatmospheric conditions including areas having rainfall or condensationfrom dew or the like. Under such atmospheric conditions acoustic portsor orifices or other openings may be blocked during the rainfall orcondensation by a water meniscus thereacross and interfere with orprevent the desired verification. It would be desirable that suchopenings be capable of passage of sound waves or free movement of gaseswithout the addition of hoods, shields, etc., or any other extensiveadditions to the base member.

Orifices are also used in fiuidic systems which may include one or moreliquids or gases under low pressure passing the orifice. A meniscusformed across the opening may obstruct or block the free movement ofgases therethrough.

SUMMARY OF INVENTION In view of the above, it is an object of thisinvention to provide a non-meniscus forming orifice.

It is a further object of this invention to provide an orifice whichtends to clear itself of any fluids which may attempt to produce ameniscus thereacross.

Various other objects and advantages will appear from the followingdescription of the invention, and the most novel features will beparticularly pointed out hereinafter in connection with the appendedclaims. It will be understood that various changes in the details andarrangements, which have been herein described and illustrated in orderto explain the nature of the invention, may be made by those skilled inthe art.

The invention comprises a member having an opening therein with a notchin the member having a wide portion substantially tangent to the side ofthe opening and converging edges from said wide portion.

DESCRIPTION OF DRAWING The invention is illustrated in the accompanyingdrawing wherein:

FIG. 1 is a perspective view of a member including an opening and notcharrangement made in accordance with this invention;

FIG. 2 is a cross-sectional view of an antenna system includingnon-meniscus orifices together with a schematic diagram of asurveillance system coupled thereto;

FIG. 3 is an expanded cross-sectional view of a portion of the antennasystem of FIG. 2; and

FIG. 4 is an expanded fragmentary view of a portion of the antennasystem of FIG. 2.

DETAILED DESCRIPTION The member or structure in which the orifice oropening is located and its shape, construction, configuration and thelike will depend upon its ultimate use. The member may be fiat orinclude a flat portion, as shown by base or conduit member 10 in FIG. 1,or be curved and of any appropriate thickness or cross section. Assumingthat member 10 is a thin sheet and is shown with exaggerated thickness,the non-meniscus forming orifice of this invention may be formed asillustrated in FIG. 1. The opening which is subject to meniscus blockingmay be annular of any desired circular or non-circular shape, dependingon its use. In base member 10, opening 12 is shown as circular forpurpose of illustration. A notch 14 is provided in base member 10 havinga wide portion substantially tangent to the sides of orifice 12 and withedges 16 and 18 converging together to a vertex away from the points oftangency. Since base member 10 is assumed to be a thin sheet, notch 14is shown as a complete cutout through base member 10. If base member 10has sufficient thickness, notch 14 may be made of varying depths andconfigurations to provide the desired meniscus freeing action asillustrated with respect to FIGS. 2-4. Notch 14 may have vertical,slanting or curved walls so long as edges 16 and 18 are maintained withsufficiently sharp configuration or definition to insure effectivewetting thereof by the fluid being cleared from opening 12. The sharperthe edges the greater the wetting action. Such notches or grooves may beappropriately formed in the base member by cutting or machining or byother processes if the converging edges are maintained in the desiredsharp configuration.

Any appropriate fluid pressure responsive or similar utilization means,device or system may be coupled to one or both sides of opening 12 toutilize the opening for passage or use of some desired fluid.

The length of edges 16 and 18 is preferably at least as long as thediameter of opening 12 to insure optimum operation of the non-meniscusforming orifice. For applications using a thin sheet base member thelength of edges 16 and 18 preferably does not exceed twice the diameterof orifice 12 though such a limitation is less significant than theminimum dimension and may not be applicable to those applications wherenotch 14 does not go entirely through base member 10.

As a fluid flows over the surface of base member 10, such as water fromrainfall, condensation or the like, a meniscus which attempts to formover opening 12 will be pulled by capillary action of notch 14 andwetting action of edges 16 and 18 immediately from opening 12maintaining opening 12 at least partially open at all times. Thus, theopening of opening 12 and notch 14 and the edges 16 and 18 combine toprovide a nonmeniscus forming orifice. It will be apparent, that suchaction will only continue while the volume of fluid is below that whichwould submerge the entire orifice and notch.

This meniscus self-clearing action may be enhanced by aligning notch 14with the vertex thereof in the direction of some force which also maytend to clear the liquid from the orifice. Such forces may includegravity or a flow of air, liquid or gas along member 10. The notch andedge arrangement is capable of overcoming to a certain extent suchforces so that, if the application requires it, the notch may be alignedin other directions and still obtain some meniscus clearing action, evenwith the notch directed in the opposite direction to the forces.

Where the liquid to be cleared is water in air, the non-meniscus orificeinhibits formation of a water meniscus with opening diameters of fromabout 0.25 down to 0.08 inch. Above 0.25 inch diameter the formation ofa water meniscus is generally not a problem while below 0.08 inchdiameter the forces of adhesion and surface tension may be too great inmany applications to be upset or overcome by variation in orifice shapewith degree of reliability.

ln the embodiment shown in FIG. 2, the conduit member or structure is anelectrically insulative, electromagnetic wave transparent, antennahousing 20 having a generally annular, conical configuration. Antennahousing 20 includes an acoustic channel, passageway or duct 22 passinglongitudinally therethrough from a microphone or other sound or fluidpressure responsive transducer 24 in the base 26 of the housing to oneor more transverse openings 28 and 30 which communicate between duct 22and the exterior of housing 20. Openings 28 and 30 may be of anyappropriate circular or non-circular shape and of any convenient openingorientation. The openings 28 and 30 include a notch and edge arrangementsimilar to that described with respect to FIG. 1 but with a Vshapedgroove configuration 32 and 34, which is shown in greater particularityin F IGS. 3 and 4. The edges of the V-shaped grooves 32 and 34 convergefrom the wide portion, tangent to openings 28 and 30, to a vertex. Asshown in FIG. 4, the opening and V-shaped notch and groove cooperate toprovide the non-meniscus forming orifice. Antenna housing 20 may bearranged in many applications in a generally vertical position withgrooves 32 and 34 downwardly disposed so as to be aligned with liquidflow caused by gravitg.

ntenna housing 0 may also include therein appropriate receiving andtransmitting radio antennas 36 and 38 and radiation reflectors or groundplane elements 40 to provide contact with some appropriate remotelylocated monitoring station. These antennas may be coupled to a suitableseismic surveillance system 42 or other utilization means which monitorsseismic signals in the vicinity of system 42. Should seismicsurveillance system 42 detect seismic signals which may beman-associated, the remote monitoring station may be informed of suchthrough transmitting antenna 38. If the monitoring station agrees, itmay activate an appropriate acoustic verification system 44 throughreceiving antenna 36. Acoustic verification system 44, which is coupledto the microphone or other appropriate sound transducer 24, may receiveacoustic signals passing through openings 28 and 30 and duct 22 and bysuitable filters, receivers, audio amplifiers and the like may transmitradio signals via transmitting antenna 38 to the monitoring stationwhich are representative of any acoustic signals or sound waves pickedup by openings 28 or 30 and sensed by microphone 24.

During this operation, rain or condensation which may be formed onantenna housing 20 will be quickly cleared from openings 28 and 30 bythe non-meniscus forming orifice arrangement. Such orifices havemaintained openings 28 and 30 clear even in rainfalls of 3 inches perhour or more without obstructing the passage of sound waves tomicrophone 24. Without the non-meniscus forming orifice, such rainfallsrapidly blocked or interfered with passage of sound waves and continuedsuch blockage throughout the rain. This selfclearing action of fluidfrom the opening was achieved without additional fluid shielding of theopenings.

What is claimed is:

1. Apparatus comprising acoustic pressure responsive means, an antennahousing member having an acoustical duct therein in communication withsaid acoustic pressure responsive means, said antenna housing memberhaving a wall portion with a passageway therein communicating with saidacoustical duct and including an orifice exposed to the exterior of saidhousing and a notch with a wide portion substantially tangent to thesides of said orifice and with edges converging from said wide portionand in general alignment with normal direction of liquid flow along saidantenna housing member.

2. The apparatus of claim 1 wherein each of the converging edges of saidnotch is of length greater than diameter of said orifice.

1. Apparatus comprising acoustic pressure responsive means, an antennahousing member having an acoustical duct therein in communication withsaid acoustic pressure responsive means, said antenna housing memberhaving a wall portion with a passageway therein communicating with saidacoustical duct and including an orifice exposed to the exterior of saidhousing and a notch with a wide portion substantially tangent to thesides of said orifice and with edges converging from said wide portionand in general alignment with normal direction of liquid flow along saidantenna housing member.
 2. The apparatus of claim 1 wherein each of theconverging edges of said notch is of length greater than diameter ofsaid orifice.